The present invention relates to a method of controlling a duplex page printer operating in such a manner that a printing operation is first performed for the first surface of each of a plurality of sheets of paper which are successively supplied from a paper feed mechanism to a printing part, the sheets of paper are then sent to a paper transfer path having a paper turning-over mechanism, to be sent back to the printing part, a printing operation is performed for the second surface of each sheet of paper, and then the sheets of paper are sent to the outside (e.g. U.S. Pat. No. 4,116,558 may be referred to for such a printer).
A conventional printing controller for a duplex page printer capable of transferring a plurality of sheets of paper (for example, five sheets of paper) at the same time, is provided with a full-dot memory capable of storing printing data for ten pages in the form of dot patterns. In more detail, printing data including form information and printing letter data is sent out from the channel on the host side, and is converted into dot patterns, to be stored in the full-dot memory. When the printing data for ten pages is converted into dot patterns and the dot patterns are stored in the memory, the duplex page printer is activated, and a paper feeding operation and a printing operation are started.
In such a control method, however, a time interval between a time the printer controller begins to receive the printing data and a time the printer begins to perform a printing operation, becomes long. Specifically, in a case where it takes a lot of time to convert the printing data for at least one page of a plurality of sheets of paper into a dot pattern, the start of the printing operation will be greatly delayed, even if printing data for the remaining pages can be converted into dot patterns in a short time. Further, printing data for the following pages cannot be converted into dot patterns till the full-dot memory becomes empty. Accordingly, the conversion of the printing data for the following pages into dot patterns is delayed by an amount corresponding to the delay in start of printing operation, and thus a time necessary for performing a printing operation for a predetermined number of sheets of paper will be increased.